Designing a finless surfboard from first principles

A couple of weeks ago I pulled up to the beach for a quick surf. It was small but peeling nicely. I had only put one board in the van. A 6’0" Pavel fish that I hadn’t ridden in a year since I discovered Geoff McCoy. However as I had met Rich recently I decided to give his board a go. So I pull the board out and go to put the fins on, only to find that I don’t have the little lokbox steel plates. So for the first time ever I tried surfing finless.

 

Wow I was blown away, it feels like nothing else so smooth and fast. I did manage to stand up for a few seconds . It’s a lovely feeling and I want more. Looking at Derek Hynd surf he makes it so effortless, however he is really nursing it and I don’t think my knees would take that amount of sustained compression.

Looking at the options out there at the moment they all seem to feature a large concave. I can see the benefit, however when thinking it through it seem to me that there are 2 problems to solve.

 

  1. When dropping down the wave face you want directional stability in the vertical component. It seems to me that the best way to achieve this in by increasing drag at the tail of the board by rapidly pulling in the tail like a Thumb or putting in a large amount of Vee or belly.

 

2 When trimming stabilising the tail is less important and the interaction of the rail with the wave face becomes more critical. Of all finless craft an Alaia seems to be the most stable in trim.

 

So in my mind and in APS300 my finless craft has a parallel profile 18" wide, round nose, alaia rails - ie. flat for 1.5" inboard from the rail before the volume increases. The tail in is a v shaped tail from 12" up with 3/4" vee in the bottom. The rails are neutral all the way until the last 8" where they are up rails to suck down the tail a bit. Nose rocker will be about 4" with about 1" of tail rocker

 

So no concave. I will build it, I’m just really busy at the moment, so I would love to hear your views.

 

Peace

Burnsie

“Shit-boxes
with their roofs cut off will not get you laid” -
There was gucci board around here for sale. My alaia is a more reliable lay, mo betta standing up with a smile.

I really think you oughta first fix whatever you need for the board you got.  then you can try it with small fin(s) or none at all.

My grandfather, born on Waikiki on the grounds of the Halekulani Hotel (it was his grandmother's estate) made my first board, about 7' long, 19 wide, from a plank of kiln dried redwood.  Without a fin.  Just like he used to use back in the day.

Man that thing would slide ass so bad.  As soon as you got off your belly (and sometimes even before) it wanted to slew sideways.

I've see the alaia vids on Youtube, etc. and I've seen the shots of Derek H at J-bay.  You aren't, and I aren't, Derek.  All the vids I've seen have guys pretty much in what we called the toilet bowl squat.  It ain't pretty, and compared to any kind of modern surfing, it's not gonna get you there. 

It seems that the "hot thing" in alaia construction is putting some kinda channel on the bottom.  To me, this defeats the purpose - it's just an imitation of some kinda "thing" on the bottom to induce direction, and it doesn't - much.  Don't expect it to, either.  There's just not enough there to produce any really useful directional effect.

But it does feel nice, or something, and it's different.  But it's "surfing" from a hundred years ago, and we've moved on, most of us.  For me, I just don't get enough water time to be wasting it, or the waves when I do get to go out.  And I live on the south shore of Oahu, where there's easy access to SOMETHING almost all the time. 

The concave in the alaia doesn’t work by channeling water. Because there is no fin, the water travels diagonally across the board, unlike a finned board where it travels more parallel to the stringer. The reason the concave ( combined with a rolled bottom) creates hold is because it increases the surface area of the bottom of the board without increasing the width. This creates pockets of low pressure under the board which effectively sucks the board into the face of the wave. This allows the board to trim almost parallel to the face of the wave, with minimal drag, hence the amazing speed. But this design will never really hold in for a deep bottom turn though.

“…only to find that I don’t have the little lokbox steel plates.”  Dat happened to me once several years ago but it was a missing single fin screw that sent kooky shudders to my reality after a long drive to da beach. I tried surfing anyway.

Weren’t those hot curls sporting deep v’s? Might want to check them out. Don’t know if it will help but those concaves worked on my alaias. One has a small groove through the belly in the nose down the center that leads to the concave, its a fat 1/8" wide and deep, well rounded. That board was the easiest to stand and trim with. Prone couldn’t feel the difference.

Hope you make your board, you sound like a man on a mission.

 

I'm inclined to side with Honolulu – there is this tendency in many of these 'finless' builds to emulate fin-function via some other design element. I'm also inclined to agree with his point about the evolution of surfboad design in general – there are really good reasons why modern surfboards have the characteristics they do.

That said, my fascination with finless boards arose from my interest in a minimum bottom planing surface area and optimum surface/rail geometry in stand-up surfing. As the answer was likely to vary with conditions and rider, it [the answer] was more likely to come in the form of a range.

The skimboards of skimboarders who make it into shore break are likely close to that optimum, both in terms surface area and surface/rail geometry, as are products like Morey's “The One”. The use of modern materials, have allowed many of these products to pursue a more fundamental strategy in their design. In particular, the over all geometry of the boards themselves are less driven by the need for buoyancy, but more by function as it relates to surfing. And they don't appear to need fins, nor the emulation of fin-function via some additional design element – hence they are truly modern finless beasts.

In general, because of their geometry, the rider once up on his feet, is able to control the bottom plane with sufficient ease and sensitivity, enabling both his response time and the impact of his actions to match that of the demands of stand-up surfing. In effect the surfer is surfing something close to the minimum bottom plane requirement, as opposed to a whole lot of extra stuff which has little to do with surfing, but more to do with paddling around or catching waves for that matter. (Paddling around, catching waves and surfing are virtually three different sports and each has there own unique demands. These demands may overlap to some degree, but the demands of each are still somewhat unique.)

I'm inclined to read the solution which you've offered as one that already comes with some baggage. Smack me down if you like, but it's as if you already had a board (with a particular geometry, volume, etc.) in mind, and then you started to think about how to solve the control-function for that particular virtual beastie. I'm not dissing the approach. My guess would be that this kind of approach has led to a lot of innovation, both directly and directly. If nothing else you're likely to become far more knowledgeable with respect to the subtleties of the role of drag as it applies to fin function. But, in general, the approach does have its problems, and this sort of ties back into Honolulu's post.

Modern surfboards look the way they because they have evolved.as a  'system', that is one design element here, assumes that this other design element will also be present, possible over there. These kinds of interconnections for the most part are often assumed and rarely addressed explicitly, and probably for good reason.

Consider, if I take my (shit-box?) car and buzz off the roof, would I then have a convertible? No. I'd have a shit-box with no roof. My you, on sunny days I might be able to enjoy the same pleasures that a convertible might offer – excluding any enhanced sex appeal that might actually come from driving around in a real convertible... after all it's a shit-box without a roof. The car just doesn't have the full functionality of a true convertible.

Let's say I solve part of the problem by making sure I always have an umbrella with me. Great, now if it rains I'm protected. Mind you, I'll have to drive pretty slow in the rain with the umbrella up, which is sort of dangerous where I live. Slow drivers are not very popular, if not a hazard (to the driver.) So perhaps I should carry some duck tape to secure the umbrella. …. Perhaps you can see where I'm taking this. “Shit-boxes with their roofs cut off will not get you laid”... uh, what a minute... what was the point of this post again?

kc